In Umberto Eco's novel The Name of the Rose it emerges that a number of monks have been killed by a poison placed on the corners of the books in their monastery library. This month the author discovered that modern vehicles of communication can be equally treacherous.

On receiving an honorary degree in "Communications and media culture" from Turin University, Eco warned against the unreliability of much of the information carried on Internet and suggested that schools should teach pupils how to sort the wheat from the chaff and newspapers should devote greater resources to a similar exercise.

"Social media give the right of speech to legions of imbeciles who previously spoke only at the bar after a glass of wine, without damaging the collectivity," Eco told journalists in a conversation after the ceremony. "They were immediately told to shut up, while now they have the same right to speech as a Nobel Prize-winner."

Eco is one of Europe's intellectual heavyweights, the author of a sociological analysis of mass communication, a semiotician and philosopher, who has taught at Harvard and Columbia universities.

His comments, recorded on video and posted on YouTube, risked coming across as snobbish and arrogant. Twitter commentators certainly thought so, and were quick to seek revenge.

"Social networks give freedom of speech to legions of imbeciles. With print it was only regiments," wrote one. "#umbertoeco as mad as the coachmen when the automobile started to catch on," said another.

Giovanna Cosenza, one of his former students, suggested the 83-year-old media expert had been trapped into the reply by a leading question from a journalist. But the professor also enjoyed stirring a row, she said.

"A sophisticated intellectual who can turn into a troll. Not bad at all," Cosenza wrote in a comment for Il Fatto Quotidiano newspaper.

Beppe Grillo, the stand-up comedian turned politician who has harnessed Internet communications for the service of his Five Stars Movement, was guilty of a potentially more serious Twitter slip last week.

Commenting on a controversy over the role of the mayor of Rome, Ignazio Marino, he tweeted: "Elections for Rome as soon as possible. Before the city is submerged by rats, trash and clandestine migrants #marinoresign."

The apparently racist message was pounced on by other Twitter users and was quickly changed to read "rats, trash and migrant camps run by the mafia."

Once again, fellow Twitter users were quick to go on the attack. "OK the correction, but we need an apology for the hyperbolic stupidity written earlier," said one. "@beppe_grillo this is your consideration for the lives of men compliments," wrote another.

Perhaps the most wounding tweet read: "Rome risks being submerged by rats, trash and Grillo. (Not that I want to place them on the same level, eh)."

It was a relatively unusual gaffe for Grillo, who is a skilled communicator and author of one of Italy's most widely read blogs, where he had published an effective analysis of the troubled political situation in the Italian capital.

The two episodes revealed not so much that even media gurus can blunder in their communications, but that Twitter offers a swift reply from the "imbeciles" when they do.

The 140-character messages can also play a healing role.

France's Environment Minister Segolène Royal chose the medium to issue an apology after calling for a boycott of Italy's Nutella chocolate and hazelnut spread, which she said in a television interview contributed to deforestation through its use of palm oil as an ingredient.

Italian authorities responded angrily and Ferrero, the manufacturer, insisted all its palm oil was responsibly sourced.

"A thousand apologies for the polemic on #Nutella. Let's agree to put the emphasis on progress," the minister wrote in a placatory tweet last week.

From reputational damage to international diplomatic repairs, the short messages have shown their power to move public opinion in a country famed for the impulsiveness and volubility of its people.

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